I would advise against wasting *5 food/chicken on Elhain. She was my starter, and I dare say she is the best out of the four for early game, she really shined, and she still does pretty well at *5/50 in Faction Crypts, but if you get enough blue shards, you are bound to get Athel (my personal favourite) or Kael sooner or later. Those are the ones worth six-starring and are good farmers. You may even get someone better if you are lucky.

I have Turvold and Ghostborn already 6 starred.

Besides the candidates I listed in my previous post, here are some the ones I am sitting on:

Occult Brawler

Shaman

Catacomb Councilor (not going to use him in the fusion, just don't have the time to do it)

Warcaster

Those are the only other ones worth mentioning. 

Thanks!

Why don't you try farming campaign with Ghostborn instead of Turvold? He has AOE attacks, should go much faster. You do definitely need somebody to farm 12-3, but I should think Ghostborn can do it. 

Both High Khatun and Apothecary can really do a lot of their work already at 5 star, taking them to 6 star isn't really urgent though you'd want to do so eventually. I would vote for Sinesha instead, who is amazing almost everywhere, near the top of my wishlist (or, well, the semi-realistic wishlist anyway). Reliquary Tender is considered among top ten or so rares I think, definitely a good champion to have. 

I think you are right with High Khan and Apothecary not HAVING to be 6 starred as they seem to be doing what they do best already at 50. 

I've tried farming 12-3 brutal with Ghostborn and I just don't have the gear yet for him to make it through the last wave, same with Turvold, hence why I am farming 11-1 (not as much XP or silver as 12-3, but it's something). Once I get better gear, I will give him a shot again.

I think you may have convinced me on Sinesha. I know she's not great at Clan Boss, but rocks everywhere else. Maybe she should go ahead in the line.

What do others think? Thanks for all of your thoughts!